Calpionellids are an extinct group of
eukaryotic
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
single celled organisms of uncertain affinities. Their fossils are found in marine rocks of
Upper Jurassic to
Lower Cretaceous age.
They were
planktonic organisms with
urn-shaped,
calcitic tests that had a widespread distribution across the
Tethys Ocean from the late
Tithonian
In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
to the early
Valanginian
In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 137.05 ± 0.2 Ma and 132.6 ± 0.2 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretac ...
and were characterised by rapid evolution, and their abundant remains in deep sea sediments from this interval are important as they allow long distance
biostratigraphic correlation and precise dating. Calpionellids were not confined to the Tethys, as they have also been found in the
Vaca Muerta of northern
Patagonia, in what was then the southeastern Pacific. Calpionellids are divided into two main families, the Chitinoidellidae, which are the earliest members of the group, appearing in the mid Tithonian, characterised by
microgranular lorica. Calpionellidae appear later, including widespread genera such as ''
Calpionella'' and ''
Calpionellites,'' and have combined microgranular and
hyaline lorica. A third family, the Semichitinoidellidae are sometimes recognised.
Naming
The name is derived from the Greek "κάλπις", meaning "water jug".
References
Alveolata families
Prehistoric eukaryote families
Fossil protists
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